Booster seat



FIG. 1 ia a front elevational view of a child's booster seat showing the design of my invention;

FIG. 2 is a left side elevational view;

FIG. 3 is a rear view;

FIG. 4 is a right side elevational view;

FIG. 5 is a top view; and

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a booster seat, as shown and described. 